/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2006, Red Hat Middleware LLC, and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.jboss.web.tomcat.servlets;

import java.io.IOException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletContext;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletConfig;

import org.jboss.logging.Logger;

/**
 * A generic fowarding servlet that obtains the ServletContext for the
 * forwardContext init-param and then obtain a request dispatcher for the
 * request.getPathInfo and forward the request. This allows a global servlet
 * mapping to redirect requests to a common target. An example would be a
 * global web.xml error-pages with a single shared context for the web
 * pages. This requires that the web context crossContext attribute is set to
 * true.
 * 
 * @author Scott.Stark@jboss.org
 * @version $Revision: 60880 $
 */
public class ContextForwardServlet extends HttpServlet
{
   /** @since 4.2.0 */
   static final long serialVersionUID = 5887848400339603842L;
   
   private static Logger log = Logger.getLogger(ContextForwardServlet.class);
   /** The name of the context to which requests are forwarded */
   private String forwardContext = "/error-pages";

   public void init(ServletConfig config) throws ServletException
   {
      super.init(config);
      String param = config.getInitParameter("forwardContext");
      if( param != null )
         forwardContext = param;
   }

   /**
    * Lookup the ServletContext associated with the forwardContext init-param
    * and then obtain a request dispatcher for the request.getPathInfo and
    * forward the request. This allows a global servlet mapping to redirect
    * requests to a common target.
    * 
    * @param request
    * @param response
    * @throws ServletException
    * @throws IOException
    */ 
   protected void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException
   {
      boolean trace = log.isTraceEnabled();
      if( trace )
      {
         log.trace("["+forwardContext+"], PathInfo: "+request.getPathInfo()
            + ", QueryString: "+request.getQueryString()
            + ", ContextPath: "+request.getContextPath()
            + ", HeaderNames: "+request.getHeaderNames()
            + ", isCommitted: "+response.isCommitted()
         );
      }
      String path = request.getPathInfo();
      ServletContext sc = getServletContext().getContext(forwardContext);
      if( sc != null )
      {
         if( trace )
            log.trace("Found ServletContext for: "+forwardContext);
         RequestDispatcher rd = sc.getRequestDispatcher(path);
         if( rd != null )
         {
            if( trace )
               log.trace("Found RequestDispatcher for: "+path);
            rd.forward(request, response);
            return;
         }
      }
      throw new ServletException("No RequestDispatcher for: "+forwardContext+"/"+path);
   }

}